From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tyrel Datwyler Subject: Re: [PATCH] of: introduce event tracepoints for dynamic device_node lifecyle Date: Wed, 19 Apr 2017 14:13:50 -0700 Message-ID: <5aa699db-255a-773b-7d60-3c6f05e88050@linux.vnet.ibm.com> References: <1492475525-10827-1-git-send-email-tyreld@linux.vnet.ibm.com> <87y3uw66y5.fsf@concordia.ellerman.id.au> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <87y3uw66y5.fsf@concordia.ellerman.id.au> Sender: linux-kernel-owner@vger.kernel.org To: Michael Ellerman , Oliver O'Halloran , Rob Herring Cc: "devicetree@vger.kernel.org" , linuxppc-dev , "linux-kernel@vger.kernel.org" , rostedt@goodmis.org, Ingo Molnar , Tyrel Datwyler , Nathan Fontenot , Frank Rowand List-Id: devicetree@vger.kernel.org On 04/19/2017 03:13 AM, Michael Ellerman wrote: > Oliver O'Halloran writes: > >> On Wed, Apr 19, 2017 at 2:46 AM, Rob Herring wrote: >>> On Mon, Apr 17, 2017 at 7:32 PM, Tyrel Datwyler >>> wrote: >>>> This patch introduces event tracepoints for tracking a device_nodes >>>> reference cycle as well as reconfig notifications generated in response >>>> to node/property manipulations. >>>> >>>> With the recent upstreaming of the refcount API several device_node >>>> underflows and leaks have come to my attention in the pseries (DLPAR) dynamic >>>> logical partitioning code (ie. POWER speak for hotplugging virtual and physcial >>>> resources at runtime such as cpus or IOAs). These tracepoints provide a >>>> easy and quick mechanism for validating the reference counting of >>>> device_nodes during their lifetime. >>> >>> Not really relevant for this patch, but since you are looking at >>> pseries and refcounting, the refcounting largely exists for pseries. >>> It's also hard to get right as this type of fix is fairly common. It's >>> now used for overlays, but we really probably only need to refcount >>> the overlays or changesets as a whole, not at a node level. If you >>> have any thoughts on how a different model of refcounting could work >>> for pseries, I'd like to discuss it. >> >> One idea I've been kicking around is differentiating short and long >> term references to a node. > > I actually did this a long time ago, but balked at the size of the patch > to do the conversion. Let me see if I can find it lying around ... It would be interesting to revisit this, and toss around any other ideas anyone may have. -Tyrel > > cheers > -- > To unsubscribe from this list: send the line "unsubscribe devicetree" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >